The invention generally relates to vacuum holding apparatus and more particularly relates to vacuum holding apparatus having at least one base and a suction unit supported by the base, on which the workpiece to be held can be placed.
Suction units are known which are connected to a vacuum source by means of a hose. Such suction units can be fastened on the base either by means of a vacuum or mechanically (e.g. fastening claws, fastening cylinders and clamping screws etc.). In the case of mechanical fastening, however, the clamping device must be able to absorb all the transverse forces. Hence, strong clamping forces are required.
A vacuum holding apparatus is known from WO 99 20 437 A1. In this vacuum holding apparatus, the base has a vacuum support on which the suction unit can be placed. If a first vacuum is applied to this vacuum connection, then the suction unit is fastened to the base via this vacuum. Onto the suction unit, a workpiece can be placed which is also held in place by means of vacuum. For this purpose, the vacuum already applied to the suction unit is increased until the pressure control valve in the suction unit opens, so that the vacuum is also present in the upper holding region facing the workpiece. The suction units can then be displaced freely on the base or placed on the base in any desired manner when no vacuum whatsoever is present at the suction unit. In particular, the use of spreader beams on which the suction unit can be displaced may lead to the disadvantage that during the use of several suction units, one or another unit may become unintentionally displaced during the positioning of the workpiece or during the positioning of other suction unit. The vacuum holding the suction unit in place can be applied only when the suction units are in the required positions. A displacement of the fastened suction unit is no longer possible.
For this reason, it is the object of the invention to make available a vacuum holding apparatus in which the suction units are held on the base by means of vacuum and the workpiece is held in place at the suction unit by means of vacuum, as in the prior art, but the suction unit, while being positioned on the base, has a certain protection against displacement even when vacuum has not yet been applied.
This task is accomplished in accordance with the invention in that in the vacuum holding apparatus of the initially mentioned type, the suction unit is provided with at least one mechanical holding means for attachment on the base.
Due to the additional mechanical holding means, at times when no vacuum has been applied, sliding of the suction unit is prevented since it is connected to the base via the mechanical holding means. These mechanical holding means may be such that they only produce holding forces which are relatively low but sufficient for the assembly process.
In a farther embodiment, it is provided that the base is in the form of a spreader beam and has at least one longitudinal side a longitudinal groove extending in the longitudinal direction and that the holding means are in the form of locking means. With such an arrangement, the suction unit can be placed without special manipulations on the spreader beam from above and can be interlocked with it, where the locking means engage with the longitudinal groove.
Advantageously, on both longitudinal sides of the spreader beam, longitudinal grooves are located with which respective the locking means engage.
In a further embodiment, the locking means are provided with a spring-loaded rest position, wherein particularly the rest position corresponds to the locking position. This has the essential advantage that the locking can take place already upon placement of the suction unit on the base. A release of the suction unit takes place by means of a manual unlocking, i.e. by means of a manual operation of the locking means. It is also contemplated that the release of the suction unit can take place mechanically, for example, by means of a tool-changing system.
In one embodiment, the holding means is in the form of a pivotable clamping lever. Here, the clamping lever has, in particular, a holding arm that engages with the base and a guide rod opposite the pivot bearing point. The holding arm, during the placement of the suction unit on the base, is at first deflected and then locks itself into the longitudinal groove. This locking position is maintained in that the holding arm, in particular, is integrally connected to the guide rod and the guide rod is spring-loaded. By means of an appropriate selection of the lever conditions of the holding arm and the guide rod, the holding forces can be optimized. The spring may be in the form of a compression spring, leg spring or synthetic spring.
A simple sliding of the suction unit onto the base and thereby a problem-free deflection of the holding arm from the rest position is achieved in that the holding arm has a load ramp. The holding arm is deflected across this load ramp and, upon placement of the suction unit on the base, locks into the desired locked position, in which a load catch engages with the longitudinal groove.
Preferably, the clamping lever is attached by way of a hinge at the suction unit. This hinge makes possible a problem-free deflection of the clamping lever, wherein the hinge may be in the form of a film hinge. In one example, the clamping lever is injection-molded onto the suction unit.
In a preferred embodiment, the two gripping surfaces are connected to each other with a pressure-control valve, wherein a vacuum can be applied to the second gripping surface and the pressure-control valve opens at a certain vacuum. This suction unit may be held mechanically prior to being held by means of vacuum.